Exposure Definition in Case-Control Studies of Cervical Cancer Screening: A Systematic Literature Review

Area of Science:

• Oncology
• Preventive Medicine
• Epidemiology

Background:

• Evaluating cervical screening effectiveness requires clear definitions of patient exposure.
• Varied definitions complicate the assessment of screening's impact on cervical cancer incidence.

Purpose of the Study:

• To systematically review and describe the range of cervical screening exposure definitions used in effectiveness studies.
• To identify methodologic differences in these definitions that may affect reported associations between screening and cervical cancer.

Main Methods:

• Systematic review of case-control studies in population-based cervical screening settings.
• Qualitative synthesis of screening exposure definitions and methodologic variations.
• Searched three electronic databases (2012-2018) and included articles from a prior review.

Main Results:

• Forty-one case-control studies were included, identifying six distinct screening exposure definitions.
• Cervical cancer risk decreased significantly with different definitions: 66% (ever tested), 77% (time since last negative test), and 79% (≥2 previous tests).
• Methodologic variations included reference group composition and exclusion of diagnostic/symptomatic tests.

Conclusions:

• Standardized consensus guidelines for cervical screening exposure definitions are necessary.
• Standardization will enable accurate measurement of screening impact, especially with the shift from cytology to HPV-based screening.
• Consistent definitions are crucial for comparing cervical screening program effectiveness.